This document provides an overview of the architecture of an eSobi club application based on J2EE. It describes the various software layers including the presentation layer, domain object layer, data access object layer, business logic layer, deployment layer, and business delegate layer. It also covers domain object and table schema designs as well as components and APIs that are ready or ongoing for development following a top-down and bottom-up approach. The document emphasizes best practices for naming conventions, SQL syntax, logging, performance tuning, testing, and references core J2EE patterns.

1. Architecture of eSobi club
based on J2EE
Allan Huang @ eSobi Inc.

2. Agenda



Software Layers for J2EE Application
Table Schema structure and Domain Object
design
Look from Top-Down, Carry out from BottomUp

3. Software Layers for J2EE Application
Business Delegate Layer
Deployment Layer
Business Tier
Business Logic Layer
(Business Object)
Integration Tier
Data Access Object Layer
Architecture Component Layer
(Framework)
Domain Object Layer
(Domain Model / Entity)
Presentation Layer
(Servlet / JSP)
Presentation Tier

4. Architecture Component Layer



Generic application utilities
Often, these objects are good candidates for
enterprise-wide use
Well-known open source projects

Jakarta commons, dom4j, log4j, xerces, quartz,
java mail, jasypt, captcha …

5. Domain Object Layer


Lightweight structures for related business
information
Enterprise Java Bean



BMP Entity Bean (EJB1.0)
CMP Entity Bean (EJB2.0)
POJO (EJB3.0)

6. Ratings of Data Persistence Methods
Goal
JDBC
EJB/BMP EJB/CMP
JDO
O/R Tool
Min Learning curve
High
Low
Low
Medium
Medium
Min Code and
configuration
Low
Low
Low
Medium
Medium
Max Ability to tune
High
Medium
Low
Low
Low
Min Deployment effort
High
Low
Low
Medium
Medium
Max Code portability
Medium
Medium
High
High
High
Min Vendor reliance
High
Medium
Medium
Medium
Low
Max Availability and
fail-over
Low
High
High
Low
Low
Manageable via JTA
Yes
Yes
Yes
Yes
Yes

7. Data Access Object Layer

Encapsulate data access and manipulation in
a separate layer



DB CRUD, File, XML, FTP Server, Mail Server ...
1:1 correspondence between VO and DAO
Traditional JDBC DAO vs. Spring DAO Bean

Aspect-oriented programming (AOP)


Cross-cutting concerns
Inverse of Control (IOC)

8. Business Logic Layer





Manages business processing rules and logic
Maximize the possibility of reuse
Access Business Objects (BO) via Service Locator
(Pattern)
Stateless Session Bean vs. Spring Bean
Fast Lane Reader (Pattern)


A more efficient way to access tabular, read-only,
potentially stale data
Transfer Object (Pattern)


Carry any multiple data elements across a tier
Previously known as Value Object (is not Pattern) ?

9. Deployment Layer



Publishes business object capabilities
Web Server (e.g. Tomcat) acted business
client, Application Server (e.g. Weblogic)
acted business server
Remote session bean, Message-driven bean,
RMI service, Web service, CORBA service ...

10. Features of Deployment Wrapper Types
Feature
EJB
Web
Service
JMS
RMI
HTTP
CORBA
Caller platform
requirements
Javacomplaint only
Any
Any
Javacomplaint only
Any
Any
Communication
method
supported
Synch. only
Both
Both
Synch. only
Synch.
only
Synch.
only
Tight
Loose
Loose
Tight
Loose
Loose
Local and JTA
Local and JTA
Local
Local
Local
Local
Requires J2EE
container?
Yes
No
No
No
No
No
Supports
clustering for
scalability and
availability?
Yes
Yes
Yes
No
Yes
Yes
Coupling
Transaction
support

11. Business Delegate Layer


Hide clients from the complexity of remote
communication with business service
components
Service Locator (Singleton)


Transparently locate business components and
services in a uniform manner
Class BeanFactoryLocator or
ApplicationContext of Spring Context

12. Presentation Layer




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Controls display to the end user
Servlet 2.4 & JSP 2.0
Servlet & Java Bean (View Object)
JSP & Tag library
JavaScript & DHTML & CSS

Asynchronous JavaScript And XML (AJAX)

13. AJAX





Only reload some part and difference of web
page each time the user requests a change
A implementation of design style, not a
framework
Consists of HTML, JavaScript, DHTML, and
DOM, is an outstanding approach
Help you to transform clunky Web interfaces
into interactive AJAX applications
AJAX Web or AJAX Application ?

14. Table Schema structure and Domain
Object design

15. User-centric Tables & Classes


ER Diagram
Class Diagram

Table per subclass




User, Supervisor, Member
MemberFeed, SubscribeFeed, FavoriteFeed,
RecommendFeed, BackupFeed
1:1 Lazy initialization between Member and
MemberProfile
Nested MemberFolder


Tree structure
4 default folders per member

16. Feed-centric Tables & Classes


ER Diagram
Class Diagram
 Nested FeedCategory


Nested RecommendReply






Tree structure
While malicious of Reply == true, this reply would be removed from
user’s view
FeedRecommend


Tree structure
While malicious of Recommend == true, this reply would be removed
from user’s view
FeedTagCase between PublicFeed and FeedTag
FeedVote between PublicFeed and User
RecommendVote between FeedRecommend and User
M:M between FeedTag and FeedRecommend

17. Mail-centric Tables & Classes


ER Diagram
Class Diagram

OutMail & InMail



While trashed of OutMail == true, this mail would be
removed from sender’s view
While trashed of InMail == true, this mail would be
removed from receiver’s view
While one trashed of OutMail == true and trashed of it’s
InMails == true simultaneously, these mails will be
deleted from database

18. My Space-centric Tables & Classes


ER Diagram
Class Diagram



MySpaceSetting between MySpace and
MySpaceChoice
MySpaceAnswer between MySpace and
MySpaceQuestion
1:1 Lazy initialization between MemberProfile and
MySpace

19. Access Control-centric Tables & Classes


ER Diagram
Class Diagram

Table per class hierarchy



Nested Group




AccessControl, UserControl, RoleControl, GroupControl
AccessRule, SupervisorRule, MemberRule
Tree structure
M:M between Role and User
M:M between Group and User
Access Rule


Priority UserControl > RoleControl > GroupControl
Resolves conflicts when the same type of AccessControl are
assigned

20. Forum-centric Tables & Classes


ER Diagram
Class Diagram

Nested TopicReply



Tree structure
While malicious of Reply == true, this reply would be
removed from user’s view
Topic Watch


Update last replied time when user replies
Between User and ForumTopic

21. Look from Top-Down, Carry out from
Bottom-Up

22. Ready for APIs & Components I

User Authenticator

Related Tables & Classes





User-centric
Login & Logout
Cookie mechanics
Password Digester
Random 12-characters Password Generator

23. Ready for APIs & Components II

eSobi Feed Subscriber

Related Tables & Classes




User-centric
Feed-centric
Public Feed count & Member Feed record
eSobi Feed Recommender

Related Tables & Classes


User-centric
Feed-centric

24. Ready for APIs & Components III

eSobi Folder Backup

Related Tables & Classes



User-centric
Feed-centric
eSobi Folder Restorer

Related Tables & Classes


User-centric
Feed-centric

25. Ongoing for APIs & Components I

Data Migration


Data List Handler



Parse RSS XML to find information of feed
User Authorizer


A pattern for Large Search Result Sets
Paging Controller applied to web page
RSS Parser


Old data is migrated to the new schema
According to Access-Controls to find Access-Rules
Mail Carrier

26. Java Naming Convention

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According to Java Bean convention
Attribute firstly, Getter method secondly,
Setter method lastly
Collection-type Attribute, add extra Adder and
Remover method
Convenient findXXXByZZZ method

27. SQL Syntax Convention

Statement



Spells SQL keywords in upper case
SQL statements are often broken into multiple
lines
Table & Column name


Primary key should be the table name suffixed
with "_id“
Separate words and prefixes with underlines,
never use spaces

28. Logging Service Convention




Replace System.out / System.err println with
Logger
Level warning & error & fatal on Production
machine
Level trace & debug & info on SIT / UAT
machine
Logging necessary messages about our
logic.

if log.isXXXEnabled, then log.XXX message

29. Centralized Controlling & Distributed
Computing

There’s no need to reinvent the wheel


Bitter design vs. Appropriate design


Tree traverse method
Universal entry between up-tier and down-tier


J2EE Pattern & GoF Pattern
Hard code vs. Sophisticated Algorithm


Open Source Community
e.g. Service Locator & Session Façade
Divide and conquer inside the same tier

30. Concurrent Access Risk



Deadlock while insert & update concurrently
Dirty columns of table for performance gain
AJAX seems delicious, but ...

31. Performance Issue & Tuning

High availability & High scalability



Clustering & Load Balancing
Fail Over & Session Persistence
Code Refactoring



SQL statement (DAO) Tuning
Business Logic (BO) Tuning
Cached Result Page



Event-Driven: JMS (Synchronous)
Scheduling: Quartz (Asynchronous)
Database Refactoring



Re-Index on Tables
Database Trigger
Database Stored Procedure

32. Test-driven development

Planning





Release planning creates the schedule
Make frequent small releases
The project is divided into iterations
Iteration planning starts each iteration
Designing



Simplicity
Choose a system metaphor
Refactoring whenever and wherever possible

33. Test-driven development

Coding



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
Code must be written to agreed standards
Integrate often
Use collective code ownership
Leave optimization till last
Testing




All code must have unit tests
All code must pass all unit tests before release
When a bug is found tests are created
Acceptance tests are run often

34. Reference
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Core J2EE Patterns
J2EE Patterns Catalog
GoF Patterns
AJAX Patterns
Java Naming Convention
Essential Database Naming Conventions
SQL Syntax Conventions
Extreme Programming

35. Q&A